There’s a bug where if the Guard Post is boosted for the attacker, the immortal gets extra health, but the health bar isn’t adjusted. So until enough damage is done to wipe out the boosted health, it looks like an immortal/minion takes no damage. Given the amount of damage done here, it’s unlikely that the person was cheating - just a display glitch. Hope that helps.

Bruce Campbells Army of Darkness - an open lv 40 guild for casual players of all levels who want to develop their dungeons and get Dreadstone in tournaments